In the existing technique, when it needs to adjust the water output of the tap or other water output devices, the user has to lift or press the tap switch, the tap switch will control the movement of the spool to reduce the water output, thus the water is saved, other tap switches may control the movement of the spool by rotating. However, no matter what kinds of manners are applied for controlling the movement of the spool, the states of two terminal movements of the tap switch are no water output and maximum water output, moreover, because the spool is in the water inlet of the tap, so when the spool is controlled to adjust the water output, it will be easy to close the water or increase the water output suddenly due to the difficult of handling the operation strength, it is not convenient for operation.